This invention relates a method for preparing aromatic heterocyclic block copolymers.
In general, aromatic heterocyclic extended chain polymers are well known for their outstanding thermal, physical, and chemical properties. Arnold et al, U.S. Pat. No. 4,108,835, disclose extended rod-like benzo-bis-oxazole and benzo-bis-thiazole polymers having superior mechanical properties as well as a high degree of thermal and hydrolytic stability. However, these materials presented special processing problems because of the extended-chain, rigid-rod, structural character of their molecules.
In accordance with the invention defined in U.S. Pat. No. 4,207,407, to Helminiak et al, it was found that the processing problem could be overcome by blending a coil-like, aromatic, heterocyclic polymer with a rod-like, aromatic, heterocyclic polymer. An improved method for blending coil-like and rod-like polymers is disclosed in U.S. Pat. No. 4,377,546, to Helminiak et al.
Wolfe et al, in application Ser. Nos. PCT/US82/01285 and PCT/US82/01286, both filed Sept. 17, 1982, disclose aromatic heterocyclic block copolymers made up of rigid and flexible segments. These copolymers are prepared by separating polymerizing the rigid segments and the flexible segments onto the rigid segments.
We have found that these block copolymers can be prepared by a simpler procedure.
Accordingly, it is an object of the present invention to provide a method for preparing aromatic heterocyclic block copolymers having rigid and flexible segments.
Other objects and advantages of the present invention will be apparent to those skilled in the art.